Declarative Debugging of Missing Answers in Constraint Functional-Logic Programming

It is well known that constraint logic and functional-logic programming languages have many advantages, and there is a growing trend to develop and incorporate effective tools to this class of declarative languages. In particular, debugging tools are a practical need for diagnosing the causes of erroneous computations. Recently [1], we have presented a prototype tool for the declarative diagnosis of wrong computed answers in CFLP (D), a new generic scheme for lazy Constraint Functional-Logic Programming which can be instantiated by any constraint domain D given as parameter [2]. The declarative diagnosis of missing answers is another well-known debugging problem in constraint logic programming [4]. This poster summarizes an approach to this problem in CFLP (D). From a programmer’s viewpoint, a tool for diagnosing missing answers can be used to experiment wether the program rules for certain functions are sufficient or not for computing certain expected answers. For example, consider a CFLP (H)-program fragment written in T OY [3], where strict equality and disequality constraints are used for generating family relationships based on the basic family facts shown in Fig. 1.